The quality of valuable gems such as diamonds, rubies, sapphires, emeralds and the like is determined largely in a subjective manner. More particularly, persons allegedly skilled in the art will examine a gem with a magnifying eye piece looking for flaws and the like and will then express an opinion as to the quality of the gem and its value. About the only parameter that is not subjective is the weight of the gem itself.
While the above referred to "experts" may provide fairly consistent estimates as to a gem's quality, there is often a wide variation wherein the same gem is examined by two totally different "experts". Again, about the only parameter that the two experts will find in common is the weight of the gem.
As a consequence of the foregoing manner of evaluating gems, and the fact that any estimate as to worth based on the quality of the gem is largely dependent upon the particular person analyzing the gem, great disparities can exist in proper evaluation of a gem, particularly where the evaluators themselves are widely spaced geographically or come from other countries where different techniques might be used.